The present invention relates to an axle system for the articulated arrangement of vehicle axles in motor vehicles, comprising an axle strut body and at least one joint body, wherein the axle strut body has recesses that are formed in the end regions to receive the joint body.
An axle strut body for the articulated arrangement of vehicle axles in motor vehicles is known from DE 44 41 219 A1. This document discloses two bar-shaped sections that are joined together to form a one-piece axle strut body. These rod-shaped sections are hollow sections and are produced from shell-shaped open parts. A joining technique known per se, e.g. gluing, ultrasonic or orbital welding, or elastically deformable snap elements are used to connect the shell-shaped profiles with one another to form a hollow axle strut body.
Axle strut bodies at most have to withstand static and dynamic loads, particularly regarding tensile and compressive stresses, and furthermore have to have a low rate of wear. In the axle strut body disclosed in DE 44 41 219 A1, the static and dynamic chassis forces that occur under load are introduced into the axle strut body via bearing eyes. Depending on the loading case, different compressive and tensile stresses occur in the two section elements forming the axle strut body. As a consequence of this different loading of the two section elements, different compression and/or expansion of the section elements occur depending on the loading case. This causes very high loading of the connecting area between the two section elements joined to form an axle strut body and, in the worst case, can lead to the formation of cracks or even detachment.
Furthermore, the manufacture of the axle strut body disclosed in DE 44 41 219 A1 is disadvantageous from a production engineering point of view, since the shell-shaped open section elements first have to be injection molded in a first production step and then combined into an axle strut body in a second production step.
In view of this prior art, it is the object of the invention to provide an axle system that can be produced cost-effectively and without additional work steps and that has a low rate of wear even under high dynamic and static loads.
To attain this object, the invention proposes that the axle strut body and the joint bodies each be made as a one-piece, closed hollow section, with the joint bodies being pivot type and set into the recesses of the axle strut body in a form-fit and/or friction-locked manner.
According to this technical teaching, the axle strut body consists of a closed hollow section that is made of one piece and not produced from two joined hollow section parts as is the case in the prior art. Advantageously, the joint bodies connecting the axle strut body with the vehicle also consist of a one-piece closed hollow section. Consequently, the axle strut bodies as well as the joint bodies can each be produced cost-effectively in a single production step.
The fact that the axle strut body and the joint bodies are made in one piece provides the advantage of a better force flow, so that even if loads are high, the strains occurring in the axle strut body do not result in premature failure of the axle system due to wear. Furthermore, the one-piece design of the axle strut body and the joint bodies has the advantage that the static and dynamic chassis forces occurring under load due to compressive and tensile stresses are distributed over the entire surface of the hollow section element. This eliminates peak stresses due to material junctions. Depending on the expected load conditions, both the joint body and the axle strut body can thus be dimensioned in a simple manner, since only the material to be used and the wall thickness of the hollow section have to be defined.
For a force-optimized introduction into the axle strut body of the static and dynamic chassis forces occurring under load, the joint bodies according to the invention are inserted in form-fit and/or friction-locked manner into corresponding recesses provided in the axle strut body. For this purpose, the joint bodies are pivot type and can be simply inserted into the corresponding recesses made in the end regions of the axle strut body and can be connected with the axle strut body. The pivot type design of the joint bodies has two essential advantages. On the one hand the forces introduced via the connecting components of the vehicle into the joint bodies and ultimately into the axle strut body can be redirected in a defined and especially smooth manner. Peak stresses are thus avoided. On the other hand, the pivot type design of the joint body makes it possible to design the articulated arrangement of the axle strut relative to the connecting components of the vehicle in such a way that a force is introduced either in longitudinal or transverse direction of the pivot type joint bodies. This advantage offers the possibility of orienting the axle system as a function of the space available on the vehicle.
A further advantage of the axle system according to the invention results from the fact that both the axle strut bodies and the joint bodies are made of a hollow section. This reduces the overall weight of the motor vehicle and advantageously increases the useful load weight.
According to an advantageous proposal of the invention, the axle strut body has a changing cross-sectional area in longitudinal direction. The cross-sectional area in the central region of the axle strut body is circular and in the two end regions substantially rectangular. On the one hand this shape of the axle strut body permits a uniform distribution of the stresses occurring in the central region over the entire surface of the hollow section, which in this region has a circular cross-section. On the other hand the end regions that are provided with recesses to receive the joint bodies have flat support faces for the joint bodies. Other cross-sectional areas, for example rectangular or star-shaped as well as polygonal cross-sectional areas, are also possible.
According to a further advantageous proposal of the invention, the end regions and the central region of the axle strut body lie on axes that are at an angle relative to one another. Depending on the space available on the vehicle and the expected load conditions, the axle system is thus adaptable to the specific requirements of the individual applications.
According to a further advantageous proposal of the invention, the recesses formed in the end regions have flanged collar-shaped edges. On the one hand, this creates centering surfaces for the joint bodies that are to be inserted into the recesses. On the other hand the collar-shaped edges of the recesses ensure a favorable force introduction into the axle strut body to avoid peak stresses in the area of the recesses accommodating the joint bodies.
According to a further advantageous proposal of the invention, the joint body has a changing cross-sectional area in longitudinal direction. The cross-sectional area in the central region of the joint body is circular, while the one in the two end regions is elliptical or circular. Other cross-sectional shapes are possible.
To protect the hollow spaces of the axle strut body and the joint body from corrosive media or dirt, an advantageous proposal of the invention provides that the hollow sections forming the axle strut body and the joint bodies be tightly sealed. Also, between the joint bodies inserted into the axle strut body and the axle strut body itself, sealing rings may be arranged, which also prevent corrosive media and dirt from entering.
According to a further advantageous proposal of the invention, the two end regions of the joint bodies are each provided with an adapter element to form a flat support face. The use of such an adaptor element may be required if the end regions of the joint bodies are, for example, circular and do not offer a flat support face for fastening means. In such a case a flat support face for the fastening means can be created by interposing an adapter element that is, for example, ring-shaped and has an inside contour corresponding to the outside contour of the end regions of the joint body. Other outside contours of the adapter element besides that forming a flat support face are also possible. A corresponding adapter element may be used to couple the end regions of a joint body with the vehicle parts to be connected irrespective of the outside contour.
According to a further advantageous proposal of the invention, the hollow section forming both the axle strut body and the joint bodies is made of a composite material. The material properties can be advantageously adjusted to the expected load conditions.
To produce the axle system according to the invention, the present invention provides a process in which a tubular hollow section is formed into an axle strut body or joint body by hydroforming in a single process step. To produce, for example, an axle strut body, a tubular hollow section element is expanded at both ends and provided, for example, with a rectangular cross-sectional area. In the two end regions, a recess each is made in the form of a round or polygonal opening. The edges of this recess are provided with a flanged collar-shaped border. In addition to hydroforming, other production processes, such as ASE internal high pressure forming, rotary swaging or a combination thereof can be used to produce the axle strut body or the joint bodies.
The invention for the first time proposes an axle system that is formed by an axle strut body and at least one joint body, wherein both the axle strut body and the joint body are made in one piece as closed hollow sections. This advantageously achieves weight optimization and at the same time ensures high dynamic and static loading capacity due to a deliberate utilization of material properties and geometric shapes. For a force-optimized introduction into the axle strut body of the static and dynamic chassis forces occurring under load, the joint bodies are pivot type and can be inserted in form-fit and/or friction-locked manner into the recesses formed in the end regions of the axle strut body. On the one hand this combination of joint body and axle strut body offers the advantage of a defined and especially smooth redirection of the forces via the connecting components of the vehicle into the joint bodies and ultimately into the axle strut bodies. This avoids peak stresses and advantageously increases loading and thus also the life of the axle system. The pivot type embodiment of the joint body furthermore makes it possible to design the articulated arrangement of the axle strut relative to connecting components of the vehicle in such a way that a force is introduced either directly in longitudinal or in transverse direction of the pivot type joint bodies. Hence the axle system can be oriented in accordance with the space available on the vehicle. The fact that the axle strut body and the joint bodies to be received by the axle strut body are each made in one piece has the advantage of ensuring an optimized force flow, so that the compressive and tensile stresses occurring under load due to static and dynamic chassis forces are uniformly distributed over the entire surface of the hollow sections. Premature wear-related failure of the axle system can thus be advantageously avoided. In addition, using a hollow section element for both the axle strut body and the joint bodies makes it possible to optimize the weight. As a result, the total weight of the vehicle can be reduced and the useful load weight can consequently be increased.
Further details, features and advantages of the invention will become clear from the following description and the pertaining drawings schematically depicting a preferred embodiment of the axle system, in which
FIG. 1a is a top view of an axle strut body according to a first embodiment,
FIG. 1b is a top view of an axle strut body according to a second embodiment,
FIG. 1c is a top view of the axle strut body according to FIG. 1b with ball pivots;
FIG. 2 is a sectional side elevation view of the axle strut body taken along the section line 11 in FIG. 1a, 
FIG. 3 is a sectional side elevation view of the axle strut body taken along line III in FIG. 1a, 
FIG. 4 is a side elevation view of a joint body according to a first embodiment,
FIG. 5 is a top view of the joint body according to FIG. 4,
FIG. 6 is a side elevation view of the joint body rotated 90xc2x0 relative to that shown in FIG. 4,
FIG. 7 is a top view of the joint body according to FIG. 6,
FIG. 8 is a side elevation view of a joint body according to a second embodiment,
FIG. 9 is a top view of the joint body according to FIG. 8,
FIG. 10 is a side elevation view of the joint body according to FIG. 8 with adapter elements,
FIG. 11 is a top view of the joint body according to FIG. 10,
FIG. 12 is a top view of an adapter element,
FIG. 13 is a sectional side elevation view of a joint body inserted into the recess of an axle strut body according to a first embodiment,
FIG. 14 is a sectional side elevation view of a joint body inserted into the recess of an axle strut body according to a second embodiment, and
FIG. 15 is a sectional side elevation view of a joint body inserted into the recess of an axle strut body according to a third embodiment.